Apparatus for interrupting alternating power circuits



p 3 s. F. NORTHRUP 1,871,575

APPARATUS FOR m'rsaaurrma ALTERNA'I'ING rowan cmcfi ms Filed Dec. 27. 1928 jrzaczzfor wag? Patented Sept. 13, 1932 UNITED STATES PATENT: OFFICE.

' EDWIN FITCH NOETHRUP, OF PRINCETON, NEW JERSEY, ASSIGNOR TO AJAX ELECTRO- THEBMIC CORPORATION, OF AJAX PARK, NEW JERSEY. A CORPORATION OF NEW JERSEY APPARATUS FOR INTEBRUPTING ALTEBNATIN G POWER CIRCUITS Application filed December 27, 1828. Serial No. 328,886.

My invention relates to a new methodpf breaking alternating current power c1rc u1ts.

The main pur ose of my invention 15 to provide a normal y short-circuited wave trap within the electric circuit which is to be broken, which trap is capable of receiving the surging flow of the current when the shortcircuit is interrupted.

A further purpose is to provide between two points in an alternating current power circuit a wave trap comprising tuned divided paths containing, respectively, induction and capacity, along with a short-circuit between the points of path division, to pass the current normally through the short-circuit. The circuit is opened completely by initially opening the short-circuit so that the surge of the interrupted current flow will be taken up in the capacity of the trap and in circulation about the pathof the trap, and, while this condition exists, opening the power circuit at another point outside of the trap.

A further pur ose is to provide a substantially inductionree path between two points in an alternating current power circuit, to interrupt the flow of current through this path, atthe same time substituting for the path a divided circuit having inductance in one branch and capacity in the other in tuned relation, whereby the surge due to current interruption is taken up in the wave trap circuit thus produced, and to subsequently interrupt the alternating current power circuit at another point outside of the said path.

A further purpose is to provide the change from noninductive to inductive paths by balancing the inductance of one coil against another to form a non-inductive current path through coils inductive when not so coupled and to interrupt the flow in one of the coils so that the other inductance and a capacity produce a wave trap.

Further purposes will appear in the specification and in the claim.

My invention is shown as applied to circuits supplying inductive loads.

The invention is applicable for interruption of alternating current in any quantity to apparatus for general as well as for specific uses. It is also clear that my invention is suitable for interruption of currents of high, low or medium frequency. Because of the capacity used to receive the surge of current flow the cost will vary inversely with the frequency.

I have preferred to illustrate one main form only, selecting a form which is practical, efiioient and reliable, and which at the same time well illustrates the principles of my invention.

Figures 1 and 2 are diagrammatic illustrations disclosing my invention.

In the drawing similar numerals indicate like parts.

The interruption of power alternating current has always presented more or less diificulty, because of the tendency of the current to continue as the circuit is opened, and this difiiculty has increased greatly as the magnitude of the current interrupted increases. Oil switches and all sorts of special arrangements and connections have been utilized for the purpose of overcoming this well recognized difiiculty and of preventing injury from the flow of current at the time of interruption.

My invention is intended to supply a path about which the current may surge at the time of interruption and to then interrupt the current at another point.

In the drawing any source of current supply is shown at 10 which is intended to supply current to an inductive load. The load is shown in Figure 1 as a furnace inductor presenting inductance 11 and load 11'. The circuit is tuned by condensers at 12.

These two figures are intended to cover the entire range of alternating current power circuits. The condenser across the furnace coil in Figure 1 makes the connection efi'ective in a broad sense as a current transformer but it is not my intention to rule out the use of a condenser in series with the inductive load, instead of in parallel, which would constitute in a broad sense a voltage transformer.

Theoretically a low voltage at the source may be stepped up to an infinite voltage across either the capacitor or an inductance by production of suitable conditions of resonance, and control is obtained by throwing the system out of resonance whereby any desired voltage can be obtained.

Theoretically the current magnitude can be transformed to an infinitely larger current by using parallel tuned inductance and capacity, and control of the amount of current obtained by the transformation may be eflected by throwing the system out of resonance to greater or less extent.

One of the connections to the load as at 13 is shown as directl connected whereasthe other 14 passes t rough a short-c1rcu1ted wave trap and a switch.

As long as the switch 17 is closed the power line operates just as if the trap had no existence, but when switch 17 is opened the wave trap becomes efiective to receive the surge of current accompanying the interruption and to pass this surge andsuccessive followin power impulses harmlessly about the pat s of the trap. 'While this 15 taking lace the circuit to the load is opened at anot er place, as by switch 18. It is of course more usual to open the circuit at two places in the two sides of the circuit as at 18, 18' in Figure 1: V

In Figure 1 the circuit is intended to be the same as in Figures 1 or 2 except that a slightly different wave trap is provided.

The wave trap in Figure 1 comprises two branches including a capacity 15 and an inductance 16 tuned with it, and with a second equal and opposite] wound inductance 16' preferably opposite y wound on the same core 19 as seen in Figure 2. The switch 17 opens the connections of this second inductance.

The wave trap is short circuited b a switch 17 A switch 18 is placed in the si e 14 outside the limits of the trap.

When the two inductance coils are both.

connected the fact that the two inductanccs are wound in opposite directions causes the two inductances to neutralize each other causing eflective short-circuiting of the trap through the two coils. Half the current flows through each coil. As soon as the switch 17 is opened the inductance of coil 16' ceases to neutralize the inductance of coil 16 and this coil and capacity 15 are efiective as a wave trap.

It will be noted that the removal or interruption of the short-circuit involves stopping the flow of but half the current.

When the trap is properly designed to include suflicient capacity to take up the surge of the current and is properly resonated the current rush due to interruption of the shortcircuit of the trap will be taken up in the capacity and will be circulated within the trap itself. At the same time the trap will offer an almost infiniteimpedance to passage of the main current, permitting openin of the main line circuit without any complication or difficulty.

vidual whim or particular need will'doubtless become evident to others skilled in the art, to obtain all or part of the benefits of my invention without copying the structure shown, and, I therefore, claim all such in so far as they fall within the reasonable spirit and scope of In invention.

Having thus escribed my invention, what I claim as new and desire to secure by Letters Patent is:

An alternating electric circuit comprising a furnace inductor, a capacity bridged across the inductor to tune it, a source of supply for the furnace circuit and an interrupting device in circuit with the source of supply having branches, two branches including balancing inductances, and a switch in circuit with one of the inductances, and a third branch containing capacity to "balance one of the inductances, whereby the supply current normally passes through the two inductances in parallel and when the circuit through the 5 one is opened, the surge is dissipated within the tuned circuit formed by the capacity and the other inductance.

EDWIN FITCH NORTHRUP.

CERTIFICATE OF CORRECTION.

Patent No. 1,877,575. September 13, 1932.

EDWIN FITCH NORTHRUP.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, after line 9, insert the following paragraph, I

"The above principles form the basis for reference to these series and parallel systems as being effective like voltage and current trans formers";

and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 13th day of December, A. D. 1932,

M. 1. Moore.- (Seal) Acting Commissioner of Patents. 

